In a method of the above kind described in the document FR 2 790 162, for example, the vendor's telecommunications equipment is a Minitel (registered trade mark) terminal or a personal computer (PC) connected to the Internet.
That method is undoubtedly advantageous from the point of view of purchase confidentiality.
However, it has the drawback of requiring information to be exchanged between, firstly, the purchaser and the server and, secondly, the vendor and the server, which complicates the telepayment method and furthermore has the effect of slowing down the processing of the information exchanged.
Furthermore, the above method has the disadvantage of obliging the purchaser to authenticate himself to the telepayment server by means of his microchip bank card number.
Attempts are currently underway to alleviate such lack of an instant response in exchanges between a purchaser and a vendor by providing an electronic purse system, whereby money is exchanged between a purchaser's microchip bank card and a vendor's microchip bank card. It goes without saying that the exchange must be totally secure, to prevent any possibility of fraudulent attempts to create counterfeit money. Thus, like the method described in the document FR 2 790 162 mentioned above, a method of the above kind has the disadvantage of having to use electronic signature principles that are complex to put into practice and are based on a fundamental assumption as to the integrity of electronic money storage in the microchip cards, the validity of which assumption is far from self-evident.
What is more, an electronic purse system of the above kind necessitates:                either the use of a single terminal provided with a microchip card reader and having two slots to receive the purchaser's microchip bank card and the vendor's microchip bank card, the exchange of money in this case being possible only if the purchaser and the vendor are together, which is not always possible or desirable,        or, in the case of a remote exchange of money via a network, the use of a first terminal belonging to the purchaser and having a microchip bank card reader and a second terminal belonging to the vendor and having a microchip bank card reader, the two readers necessarily being connected together.        
It must be noted that the above features are found to be not only relatively inflexible but also costly, because a card reader is used in both cases.